Air Quality Health Index

The Air Quality Health Index or “AQHI” is a scale designed to help you understand what the air quality around you means to your health. It was introduced by Ontario’s Ministry of Environment, Conservation and Parks in 2015 to replace the previous Air Quality Index (AQI). Piloted in Hamilton since 2011, Clean Air Hamilton and Hamilton Public Health Services were advocates for the development of this health-based Air Quality Index.

It is a health protection tool that is designed to help you make decisions to protect your health by limiting short-term exposure to air pollution and adjusting your activity levels during increased levels of air pollution. It also provides advice on how you can improve the quality of the air you breathe.

The AQHI is calculated using a formula that combines the concentration and the relative health impacts of three pollutants: ground-level ozone (O3), particulate matter (PM2.5/PM10) and nitrogen dioxide (NO2).  According to the Government of Canada, sulphur dioxide (SO2) and carbon monoxide (CO) were removed from the formula as they were not associated with additional health risks once the three pollutants were taken into account.

This index pays particular attention to people who are sensitive to air pollution and provides them with advice on how to protect their health during air quality levels associated with low, moderate, high and very high health risks.

The AQHI communicates four primary things:

  1. Measures the air quality in relation to your health on a scale from 1 to 10. The higher the number, the greater the health risk associated with the air quality. When the amount of air pollution is very high, the number will be reported as 10+.
  2. Assigns a category that describes the level of health risk associated with the index reading (e.g. Low, Moderate, High, or Very High Health Risk).
  3. Provides health messages customized to each category for both the general population and the ‘at risk’ population.
  4. Shows current hourly AQHI readings and maximum forecast values for today, tonight and tomorrow.

The ‘at risk’ population includes individuals at increased risk due to age or a variety of conditions; these include young children, seniors, people with existing respiratory conditions (e.g., asthma, chronic obstructive pulmonary disease (COPD), bronchitis, emphysema and lung cancer) and people with existing cardiovascular conditions (e.g., angina, previous heart attack, congestive heart failure, arrhythmia or irregular heartbeat). Those in the ‘at risk’ category are encouraged to monitor the AQHI more regularly since they are more sensitive to air pollution.

The AQHI is designed to give you this information along with some suggestions on how you might adjust your activity levels depending on your individual health risk from air pollution.

For more information on the AQHI visit:

Hamilton Public Health Services – Air Pollution & Smog

Ontario Ministry of the Environment, Conservation and Parks – AQHI Forecasts & Observations

Environment Canada  – Air Quality Health Index